(1) Field of the Invention
The invention relates to a system for controlling a hydrostatic-mechanical transmission at the time of vehicle acceleration or deceleration, that is suited for use in a tracklaying vehicle such as bulldozers, and more particularly, to a technique for reducing shocks occurring at the time of vehicle acceleration or deceleration.
(2) Description of the Prior Art One of such control systems for hydrostatic-mechanical transmissions is disclosed in Japanese Patent Publication No. 62-31660 (1987). According to the system taught by this publication, the angle of a swash plate for controlling the discharge of a pump in the hydrostatic transmission unit is adjusted according to the difference between a target engine revolution speed calculated from a throttle position and an actual engine revolution speed so as to make the actual engine revolution speed close to the target engine revolution speed.